The invention relates to a method for calculating/optimizing the diameter of a paper or board web reel.
In paper and board machines a finished web is wound into machine reels which are sought to be run to a certain, usually a maximum, diameter so as to be as large as possible in size. These machine reels are run on a slitter-winder to form customer rolls, whose desired diameter and width are determined according to the customer's demand. In other words, rolls having a width and a diameter as desired by the customer are slit out of the full-width web of the machine reel by means of the slitter-winder. One problem in connection with the methods used in prior art is that if web breaks occur in the paper machine, the diameter of the machine reel changes.
In the prior art there is known a so-called continuous-trimming running mode in which machine reels are wound into a maximum diameter regardless of customer roll diameters except in the case of grade change. On the slitter-winder, splicing is accomplished to join machine reels to one another in order to obtain customer rolls of desired diameter size. Previously, splicing was performed manually and it was troublesome and difficult, the quality of splices varied and did not meet the requirements of printing houses. Today, there is also available an automatic splicing device, which has the advantage that the diameter of the machine reel need be optimized not according to individual sets but according to the entire order for a specific paper grade. However, it is problematic in this connection that, for reasons of the runnability of the printing press primarily with a view to minimizing breaks, it is required by the printing houses that if there are splices in customer rolls their number and location shall be as specified. In that connection, in the continuous-trimming running mode, it must be possible to calculate already in connection with the winding of the machine reel the location and the number of the splices caused by the joining of the ends of the webs of different machine reels to produce customer rolls of the right size so that the splices will be at the right location in the customer roll to be wound in order that it shall meet the criteria set by the customer and the amount of broke shall be minimized. The printing houses require, for example, that there shall be no splice at a given distance from the roll bottom or from the roll surface.
Previously, a manually calculated table was used concerning the effect of the customer roll diameter and the number of sets on the diameter of the machine reel. After that, automatic systems have been created to calculate the above-mentioned matters, in which it is additionally possible to take into account the effect of bad paper in the reel and different/varying winding tension as well as the thickness of paper both in the machine reel and in the customer roll and in which it is possible to take into account the content and size of machine reels placed in intermediate storage. This kind of procedure is described, for example, in the paper Paper Machine Reel Optimization—Analysis and a Case Study read by Dusan Dapcevic and published on pages C37-C45 of the conference publication: Conference Record of the 1999 IEEE Annual Pulp & Paper Industry Technical Conference; Seattle, Wash., Jun. 21-25, 1999; 1-10.